The present invention relates to a conveyor system wherein an endless web such as a belt, film, etc. is mounted to travel around support rollers and, in particular to a tracking arrangement which enables the endless web to achieve proper tracking on the conveyor frame.
As shown in FIG. 4, conventional conveyor systems comprise generally parallel rollers 24 over which an endless web W travels. Such a web could be a conveyor belt or a product, e.g. a film, being manufactured or treated. Each roller is rotatably mounted on a stationary shaft 18 by suitable bearings. The ends of each shaft are mounted in respective side supports 14, 16 of a conveyor frame 12, the side supports being straight and arranged in parallel on opposite sides of a longitudinal axis L.
In order to ensure that the web tracks in a direction coinciding with the longitudinal axis, rather than walking toward either of the side supports, it may be necessary to skew some or all of the rollers. Heretofore, that has been achieved by mounting one end of each roller shaft in a block that is movable relative to the respective side support in a direction parallel to the longitudinal axis. By adjusting the block, the inclination of the roller relative to the longitudinal axis is changed.
An operation for producing proper tracking of a web is usually done on a trial-and-error basis. That is, the operator keeps adjusting one or more of the rollers until proper tracking is achieved. The above-described roller-adjusting system is advantageous in that it provides an infinite number of positions of adjustment for each roller. One the other hand, special tools are required for making the adjustments. Furthermore, once a number of adjustments have been made, it is difficult for the operator to remember what the original state of the rollers was, in the event that the operator wishes to return the rollers to the original state following unsuccessful attempts to produce proper tracking.
It would be desirable to provide a simpler, yet highly reliable web tracking arrangement which avoids the above-described problems.